Vehicle steering systems having more than one set of steerable wheels are known. Typically, such a steering system includes a front set of steerable wheels and a rear set of steerable wheels, both of which are controlled in response to turning of the vehicle steering wheel. A steering system having more than one set of steerable wheels is particularly useful in a large vehicle such as a truck so as to increase steering maneuverability.
A known steering system having front steerable wheels and rear steerable wheels includes a front wheel steering mechanism operatively connected with the front steerable wheels and a rear wheel steering mechanism operatively connected with the rear steerable wheels. The front wheel steering mechanism operates in response to turning of a steering member such as a steering wheel. The front steerable wheels are steered in response to operation of the front wheel steering mechanism. The front wheel steering mechanism is mechanically drivingly connected to the rear wheel steering mechanism to operate the rear wheel steering mechanism. The rear steerable wheels are steered in response to operation of the rear wheel steering mechanism.
Another known steering system having front steerable wheels and rear steerable wheels includes a hydraulic steering motor operatively connected with the rear steerable wheels. The hydraulic steering motor is connected in fluid communication with an actuatable electrohydraulic valve. The electrohydraulic valve when actuated directs hydraulic fluid to the hydraulic steering motor. Operation of the electrohydraulic valve is controlled by an electrical signal generated in response to turning of a steering member such as a vehicle steering wheel.
Still another known steering system having front steerable wheels and rear steerable wheels includes an electric motor which, when actuated, moves a mechanism for turning the rear steerable wheels. The rotation of the output shaft of the electric motor is controlled in response to an output signal from a control device such as a microcomputer. The microcomputer monitors a number of signals indicative of vehicle operating parameters and generates its output signal to control the electric motor in response to these monitored signals.